1. Field of the Invention
The present invention relates to coupling of plastic pipes and machines for welding plastic pipe and, more particularly to coupling of plastic pipes by fusion welding or through a mechanical seal and a device to perform fusion welding.
2. Description of the Prior Art
Prior to the advent of plastic pipe, most piping was made out of metal, such as copper, stainless steel or iron. The particular metal used for the piping was dependent upon the application. For example, water could be transported through copper and/or cast-iron pipes. However, acids had to be transported in stainless steel pipe. Some of the metal pipe, such as copper and stainless steel, was expensive to manufacture and install. Typically, the pipe was either brazed or welded together. In some instances, mechanical type joints were provided for pipe connections. In today""s market, all of these arrangements are expensive to manufacture and install.
Plastic pipe overcomes many of the expenses associated with metal pipe. Plastic pipe is inexpensive to manufacture and relatively easy and inexpensive to connect together. In the case of thermoplastic materials, such as polypropylene, the pipe can be welded together by providing a polypropylene sleeve with electrical heating elements embedded therein. This process is known as fusion welding. Fusion welded pipe is particularly applicable in situations where acid passes through the plastic pipe. Polypropylene pipe can be secured to each other through mechanical seals. In some applications, mechanical seals are preferable to the fusion welding.
In the past, different pipe couplings were provided for fusion sealing and mechanical sealing. This resulted in an increase in inventory required by the installer, such as the mechanical contractor or plumber, since two separate types of couplings were required, one for mechanical sealing and the other for fusion welding. Further, in the past machines have been used to weld plastic pipes.
Therefore, it is an object of the present invention to provide a single coupling for use with mechanical sealing and fusion welding of plastic pipe and a machine to weld many plastic pipes simultaneously and provide good weld joints.
The present invention is a piping system that includes a first pipe, a second pipe, a coupling, an arrangement for securing the first pipe to the coupling and an arrangement for securing the second pipe to the coupling. The first pipe is made of thermoplastic material having a first pipe first end. The second pipe is made of thermoplastic material having a second pipe first end. The coupling includes a body having a coupling first end and a coupling second end. The body has an outer surface and an inner surface. The inner surface defines a passageway and a lip positioned between the coupling first end and the coupling second end. The first pipe first end is received by the coupling first end and the second pipe first end is received by the coupling second end. The first pipe first end and the second pipe first end are positioned on opposite sides of the lip.
The pipe coupling can include pipe coupling threads defined on the outer surface of the coupling configured to engage with a nut, a first tapered inner surface adjacent the coupling first end and a second inner tapered surface adjacent the coupling second end and a plurality of circumferential rings defined on the inner surface. Axial ribs can be defined on the coupling outer surface and positioned between the threads positioned adjacent the coupling first end and the coupling second end.
The arrangement for securing the first pipe to the coupling and the arrangement for securing the second pipe to the coupling can be accomplished through a fusion seal or a mechanical seal. The fusion seal includes a sleeve made of thermoplastic material having an electrically resistive wire embedded therein and two leads attached to the electrically resistive wire extending from the sleeve. The sleeve is configured to be sandwiched between the pipe coupling and a thermoplastic pipe with the two leads extending from the piping coupling. The mechanical seal includes a flexible body received between the pipe coupling and the first pipe and a nut, the flexible body is held in place by the nut co-acting with the pipe coupling and an end of the flexible body. The nut includes inner threads that co-act with the pipe coupling threads. The nut includes an annular lip that defines a passageway configured to permit a thermoplastic pipe to pass there through, the annular lip contacts an end of the flexible body of the mechanical seal and holds the flexible body of the mechanical seal in place. The flexible body also includes a tapered portion adapted to co-act with the first tapered inner surface of the pipe coupling.
The present invention can be provided as a kit for joining thermoplastic pipe together.
Further, the present invention is a method for joining two thermoplastic pieces of pipe, that includes the steps of:
a) providing two pieces of thermoplastic pipe;
b) attaching either a fusible seal or a mechanical seal at the ends of each the pieces of thermoplastic pipe;
c) passing the ends of the pieces of thermoplastic pipe with the seals through ends of a thermoplastic pipe coupling and sandwiching the seals between the pipe coupling and the pieces of thermoplastic pipe; and
d) forming a fluid tight seal between the pieces of thermoplastic pipe and the pipe coupling by either compressing the mechanical seal with a nut co-acting with the pipe coupling or heating the sleeve until the sleeve and adjacent portions of the pipe coupling and the pipe melt.
Further, the present invention includes an electrofusion joining device for facilitating the joining of two thermoplastic pieces of pipe by electrofusion. The device includes the following: an arrangement for determining the number and size of fusion seals to be joined; an arrangement for determining the wattage necessary to join the fusion seals to the polymeric pipes and couplings; an arrangement for determining process interruptions; an arrangement for compensating for process interruptions; an arrangement for determining ambient temperature; an arrangement for compensating for ambient temperature; and an arrangement for passing electric current and stopping electric current to the fusion seals.
Further, the present invention is a method for joining a polymeric fusion seal to a polymeric pipe and coupling using the electrofusion joining device. The method includes the following steps: a) connecting a plurality of fusion seals in electrical series to an electrofusion joining device to form an electrical circuit; b) determining the electrical resistance of the electrical circuit; c) calculating the wattage necessary to pass through the electrical circuit to melt the fusion seal and adjacent material of the polymeric pipe and polymeric coupling in a fixed period of time; d) passing current through the electrical circuit for the fixed or set period of time based on ambient temperature and possible circuit interruptions and causing the fusion seal to be melted to be joined to the adjacent pipe and the adjacent coupling; and e) stopping the current and permitting the joined seal to cool.